spi: aspeed: Centralize address decoding region management

spi: aspeed: Centralize address decoding region management

The original approach to handling address decoding overlaps was to trim
the next region directly. If the next CS's decoding range was fully
overlapped by the current one, it would be forcibly closed by trimming
its size to zero. This could lead expected behavior, especially on
the platform with multiple flashes layout.

To solve improper trimming problem, this patch collects the required
address decoding size at each stage, then, (re-)arragne address decoding
region to each CS centrally with knowing the total AHB decoding size.
If a segment register cannot be updated (e.g. due to bootloader write
protection), the original value is kept to avoid breaking access and
an error is reported if the total decoding size of all CS exceeds
the total AHB decoding size.

Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
Link: https://patch.msgid.link/20251001112605.1130723-5-chin-ting_kuo@aspeedtech.com
Signed-off-by: Mark Brown <broonie@kernel.org>